The reason my friends and I moved to Discord in late 2015 or early 2016 was because it blew the competition out of the water at the time. The audio was so much better. I think screen share and face cams may not have been supported at the time, but it later was and was higher quality and a better experience than Skype or Teamspeak, IMO.
Now though, that might just be table stakes for a new service now that WebRTC is standard and the codecs have gotten better too. I'm rooting for any sort of truly solid decentralized chat (text, video, and audio) to take off. Right now, all of them have notable flaws. I also think many of them try to compete with the community aspect of Discord, which I personally don't use and thus and am a bad judge of quality. Just a way to chat with people I already know.